pairs of silicon atoms
bonded together in a barbell configuration exist in up or down states whose configurations
could be changed as shown in this supercomputer simulation by a thin metallic tip as used in
Scanning Tunneling Microscopy. Source: K. Cho, J. Joannopoulos

A single oxygen atom is made visible as a blue sphere in
this supercomputer-generated image of electronic
charge inside a silicon crystal. The oxygen atom straddles one of the
silicon bonds in the bonding lattice represented by a warm-colored
honeycomb. Source: IBM Yorktown Heights and MIT

SIMULATING REALITY

The computing revolution is dramatically transforming virtually every
aspect of our society--our work, our play, even our national security.
This revolution started with the discovery of
the transistor, the result of fundamental research in solid state
physics and the earlier development of quantum theory. The next stage,
development of complex microchips
incorporating many transistors, drew from fundamental work in physics,
chemistry, and materials science. Now applications such as smart
military weapons, delivery of consumer
services such as movies on demand, or means of transferring electronic
funds in a secure manner are incorporating new discoveries in mathematics,
engineering, and computer science.

One important frontier of the computing revolution is found in
today's powerful supercomputers, which have the ability to perform
hundreds or thousands of calculations
simultaneously (so-called massively parallel computers). Within years,
this field is expected
to cross an important threshold, when the fastest computers will be
capable of a thousand billion floating-point operations per second
(teraflops). Petaflop computers (capable of a
billion billion operations per second) may follow only a few years later.

These advances in computing technology draw heavily on fundamental
science. But science and technology are closely intertwined: the
technology is also driving forward the frontiers of science--ushering in
new fields of research and extending the limits of inquiry in
virtually all fields--which will in turn enable new technology. For
example, for the first time scientists can now begin to simulate such
complex physical and biological systems as the earth's climate, the
atomic structure of novel materials, and the molecular structure of living
cells. Applications of this new computationally-driven science will
include improved microelectronic devices and rational drug design.
Computational studies of silicon-- the semiconductor material on which
most modern computing is based--illustrate the trend. Researchers are now
beginning to simulate silicon-based materials with supercomputers,
allowing them to perform "theoretical experiments" and--using new
techniques for visualizing atomic scale structure--to "see" the results.
Physicists, for example, can now use supercomputers to understand how
oxygen impurities influence and impede the electrical
properties of silicon wafers--a problem that has plagued semiconductor
manufacturers for years. In a simulation, a researcher can introduce
oxygen molecules into a silicon lattice and watch how it throws the local
electrons into a tizzy--something no microscope can observe.
The same approach can be used to study another important problem--the
migration and diffusion of impurities within a silicon crystal. Insights
from such simulations could lead to improved manufacturing processes.

Exciting results are also emerging from studies of the surface of
silicon crystals. The outermost atomic layer seems to consist of pairs
of atoms, bonded together in a "barbell" configuration. Theoretical
experiments indicate that each barbell can exist in one of two
states--up or down. This suggests the possibility of storing bits of
data on an atomic scale--many thousands of times more compactly than in
present computer memories. Other simulations show that a thin metallic
tip, similar to those used in Scanning Tunneling Microscopy, can in
principle establish the required orientation of the surface atoms. Thus
the supercomputer simulations may lead to the development of
revolutionary new information storage technologies.

The synergy between science and technology is crucial for
developing the next generation of new technologies. Present computer
designs will reach limits dictated by the laws of physics. Can faster,
smarter machines be built to model the human brain? Can biological
components be built into computer chips? What about using individual
molecules as switches a thousand times faster than microelectronic
devices? These are the kinds of breakthrough technologies realizable
only through fundamental research--research that is itself supported by
advanced technology.